Manufacturing method for a composite sheet

Abstract

A manufacturing method for a composite sheet having excellent rigidity, no shape deformation, and excellent transparency is disclosed. By laminating a film obtained by impregnating a composite resin on a wet cake including cellulose nanofibers and glycerol, rigidity and transparency may be maximized, and a flat and thick composite sheet may be provided.

What is claimed is: 
     
       1. A manufacturing method for a composite sheet, the method comprising:
 obtaining a dispersion by mixing a cellulose nanofiber and glycerol; 
 obtaining a wet cake by drying the dispersion; 
 treating the wet cake with a solvent to obtain a treated wet cake; 
 obtaining a film by impregnating the treated wet cake with a composite resin comprising a thermosetting resin and a curing agent; and 
 obtaining the composite sheet by laminating, pressing, and curing the film, 
 wherein the wet cake is obtained by drying the dispersion for 40 hours to 60 hours in a chamber having a humidity in a range of 80% to 100%, and 
 wherein the wet cake is treated by substituting the glycerol with the solvent, and the glycerol is removed. 
 
     
     
       2. The method of  claim 1 , wherein the cellulose nanofiber is oxidized with 2,2,6,6,-tetramethylpiperidine-1-oxyl (TEMPO). 
     
     
       3. The method of  claim 1 , wherein the dispersion comprises the cellulose nanofiber and the glycerol having a ratio in a range of 2:1 to 6:1. 
     
     
       4. The method of  claim 1 , wherein the wet cake has a thickness in a range of 300 μm to 800 μm. 
     
     
       5. The method of  claim 1 , wherein the wet cake is in a semidried state. 
     
     
       6. The method of  claim 1 , wherein the solvent comprises ethanol, propanol, butanol, pentanol, hexanol, ethylene glycol, glycerol, acetone, or any combination thereof. 
     
     
       7. The method of  claim 1 , wherein the thermosetting resin comprises an epoxy resin, an unsaturated polyester resin, a vinyl ester resin, or any combination thereof. 
     
     
       8. The method of  claim 1 , wherein the pressing is performed at a pressure in a range of 100 kPa to 5 MPa. 
     
     
       9. The method of  claim 1 , wherein the curing is performed at a temperature in a range of 80° C. to 120° C. for 10 hours to 15 hours. 
     
     
       10. The method of  claim 1 , wherein the composite sheet comprises the cellulose nanofiber in an amount in a range of 40% to 60% by weight. 
     
     
       11. The method of  claim 1 , wherein the composite sheet has a thickness in a range of 0.6 mm to 2.4 mm. 
     
     
       12. The method of  claim 1 , wherein the composite sheet has a transparency in a range of 66% to 85% at 600 nm. 
     
     
       13. The method of  claim 1 , wherein the composite sheet has a flexural strength in a range of 209 MPa to 273 MPa.